The remains of the great moral philosopher reside in a university in London.

This former Masonic lodge has been transformed into part museum, part bar, all awesome.

Christ's blood preserved in a Belgian town.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The most visited, and possibly most controversial, museum in Germany.

The mark of the Devil's horns on a marble column in Milan.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

Formerly Yugoslavia's "forbidden island," this sleepy little city still holds the abandoned remains of military strongholds.

A public work of art that also provides some relief from the summer heat.

This old-school café is famous for serving coffee, chilaquiles, and the Cuban Revolution.

Frida Kahlo's childhood home, now a museum of her life and works.

A magnificent, long-abandoned castle built in the wake of the reconquest of Spain.

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

Just like in Hollywood, Madrid has also a forgotten walk of fame.

Among the oldest structures in Madrid, these Moorish walls once guarded the medieval city of Mayrit.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

The final resting place of the great navigator, or maybe his brother.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

Commonly acknowledged as the only public monument to the Devil himself.

Dedicated to a young woman who broke gender barriers at the University of Madrid.

In the fictional world of Kcymaerxthaere, celestial wonders marked a portal to a powerful route of travel at this site in Madrid, Spain.

This funky former tobacco factory is one of the most striking examples of Madrid's cultural diversity.